If the LOS light on your fiber router or ONT is blinking red, it usually means Loss Of Signal. This guide explains the likely causes, the checks you can do at home, and when the issue needs technician support. When it's green and steady, everything is fine. However, when it blinks red or stays solid red, it signifies a Loss of Signal, a problem preventing your router from communicating. Routers typically have several lights indicating the status of the power, internet connection, Wi-Fi, and other functionalities. But don't despair! This guide will walk you through the most common causes of router.